Many transmission systems employ a torque controlling element to provide a continuously variable torque or speed transmission capability. An example of such a transmission is a split torque transmission, wherein a drive train is powered by dual inputs, one of which may be a torque-controlled input, such as from a hydraulic variator. In such systems, it is generally desirable to provide an output from the variator such that the resultant actual operation of the entire transmission or other system corresponds to the expected operation. For example, a user may command a certain level of acceleration, and ideally the acceleration provided by the system matches the user's needs and expectations.
To provide control signals to the variator, some systems utilize a calibration map or torque control map that maps an actuator input pressure or pressure differential to an output torque of the variator. In this way, a commanded system output may be mapped to a desired torque, which can be mapped to one or more control signals to be applied. Such a system is shown in portions of U.S. Pat. No. 6,424,902 to Kuras entitled “Method And Apparatus For Operating A Continuously Variable Transmission In The Torque Limited Region Near Zero Output Speed.” Nonetheless, certain transient factors such as system acceleration can lead to a discrepancy between the expected and actual operation of the system.
The foregoing background discussion is intended solely to aid the reader. It is not intended to limit the innovations described herein nor to limit or expand the prior art discussed. Thus the foregoing discussion should not be taken to indicate that any particular element of a prior system is unsuitable for use within the innovations described herein, nor is it intended to indicate any element, including solving the motivating problem, to be essential in implementing the innovations described herein. The implementations and application of the innovations described herein are defined by the appended claims.